The present invention relates to an active recombinant fungal protein disulfide isomerase, compositions comprising said fungal protein disulfide isomerase, and methods for their use; a DNA construct comprising a DNA sequence encoding said fungal protein disulfide isomerase, and a vector and cell harbouring the DNA construct. Furthermore, the present invention relates to a method of preparing the fungal protein disulfide isomerase by use of both traditional and recombinant DNA techniques.
The use of protein disulfide redox agents such as protein disulfide isomerases (PDI), and thioredoxins (TRX) for various purposes has been known for some time.
Protein disulfide redox agents catalyse the general reaction:
R1xe2x80x94SH+R2xe2x80x94SH+Enzox⇄R1xe2x80x94Sxe2x80x94Sxe2x80x94R2+Enzredxe2x80x83xe2x80x83(reaction I)
where R1 and R2 represent protein entities which are the same or different, either within the same polypeptide or in two polypeptides, Enzox is a protein disulfide redox agent in the oxidised state, and Enzred is a protein disulfide redox agent in the reduced state. EC 5.3.4.1 refers to an enzyme capable of capable of catalysing the rearrangement of xe2x80x94Sxe2x80x94Sxe2x80x94 bonds in proteins and EC 1.6.4.4 and EC 1.8.4.2 is an example of enzymes catalysing the reaction with NAD(P)H and glutathione as a mediator, respectively.
This type of activity has been designated as protein disulfide isomerase, sulfhydryl oxidase, protein disulfide reductase, disulfide isomerase, protein disulfide transhydrogenase, and sulfhydryl oxidase.
Disulfide linkages in proteins are formed between cysteine residues and have the general function of stabilising the three dimensional structure of the proteins. They can be formed between cysteine residues of the same or different polypeptides.
Disulfide linkages are present in many types of proteins such as enzymes, structural proteins, etc. Enzymes are catalytic proteins such as proteases, amylases, etc., while structural proteins can be scleroproteins such as keratin, etc. Protein material in hair, wool, skin, leather, hides, food, fodder, stains, and human tissue contains disulfide linkages. Treatment of some of these materials with PDI and TRX, and a redox partner have been described previously.
The use of TRX for waving, straightening, removing and softening of human and animal hair was described by Pigiet et al. (EP 183506 and WO 8906122). Pigiet (U.S. Pat. No. 4,771,036) also describes the use of TRX for prevention and reversal of cataracts. Schreiber (DE 2141763 and DE 2141764) describes the use of protein disulfide transhydrogenase for changing the form of human hair. Pigiet (EP 225156) describes the use of TRX for refolding denatured proteins. Use of TRX to prevent metal catalysed oxidative damage in biological reactions is described by Pigiet et al. (EP 237189).
Toyoshima et al. (EP 277563 and EP 293793) describes the use of PDI to catalyse renaturation of proteins having reduced disulfide linkages or unnatural oxidised disulfide linkages, in particular in connection with renaturation of recombinantly produced proteins. Brockway (EP 272781), and King and Brockway (EP 276547) describe the use of PDI for reconfiguration of human hair, and for treatment of wool, respectively. Sulfhydryl oxidase for the treatment of Ultra-high temperature sterilized milk is described in U.S. Pat. Nos. 4,894,340, 4,632,905, 4,081,328 and 4,053,644. Schreiber (DE 2141763 and DE 2141764) describes the use of protein disulfide transhydrogenase for changing the form of human hair.
The uses of such enzymes have all been connected with reduction of protein disulfide linkages to free protein sulhydryl groups and/or the oxidation of protein sylfhydryl groups to protein disulfide linkages, and/or the rearrangement of disulfide linkages in the same or between different polypeptides, and sometimes to the use of these processes in sequence.
Protein disulfide redox agents can be divided into two main groups of enzymes, thioredoxin type (TRX), and protein disulfide isomerase type (PDI).
Both these can be modified to obtain protein engineered derivatives, chemical modifications and hybrids of TRX and/or PDI (ENG).
TRX is a 12-kDa protein having a redox-active disulfide/dithiol and catalysing thiol-disulfide exchange reactions (Edman et al., Nature 317:267-270, 1985; Holmgren, Ann. Rev. Biochem. 54:237-271, 1985; Holmgren, J. Biol. Chem. 264:13963-13966, 1989). PDI consists of two subunits, each consisting of two domains which are homologous to TRX.
TRX and PDI can be obtained from a number of sources: PDI: protein disulfide isomerases have mainly been identified from mammalian sources, such as Bovine (Yamauchi et al., Biochem. Biophys. Res. Commun. 146:1485-1492, 1987), Chicken (Parkkonen et al., Biochem. J. 256:1005-1011, 1988), Human (Rapilajaniemi et al. EMBO J. 6:643-649, 1987), Mouse (Gong, et al., Nucleic Acids Res. 16:1203, 1988), Rabbit (Fliegel et al., J. Biol. Chem. 265:15496-15502, 1990), and Rat (Edman et al., Nature 317:267-270, 1985). PDI has furthermore been isolated from yeast (Tachikawa et al., J. Biochem. 110:306-313).
TRX: Thioredoxin has been identified from bacteriophages, bacteria such as Escherichia coli (Wallace and Kusher, Gene 32:399-408, 1984) and Bacillus subtilis (Chen et al. J. Biol Chem. 262:8787-8798, 1987) and eukaryotes.
It would be desirable to facilitate the production of protein disulfide isomerase (PDI), to be able of producing both larger amounts of the enzyme and to produce it in a more economical manner than what is possible by the prior art methods.
Engineered variants (ENG) with improved properties for particular applications are also highly desirable and can be prepared by a variety of methods based on standard recombinant DNA technology:
1) by using site-directed or random mutagenesis to modify the genes encoding TRX or PDI in order to obtain ENG with one or few amino acid changes,
2) by inhibiting or otherwise avoiding dimerisation of the subunits of PDI, thus giving rise to PDI monomers,
3) by producing partial monomers of PDI or TRX, in which regions of the NH2- or COOH termini of PDI or TRX are lacking,
4) by creating hybrids of PDI, TRX and/or ENG,
5) by chemically or enzymatically modifying the products of 1)-4),
6) by a combination of any of 1)-5).
ENG produced according to 1) were described by Lundstrxc3x6m et al. (J. Biol. Chem. 267:9047-9052, 1992) and by a combination of 3) and 5) by Pigiet (WO 8906122).
PDI, and TRX can, apart from their natural sources, be obtained by expression of recombinant DNA encoding plant, animal, human or microbial PDI, or TRX, in various hosts, such as microorganisms followed by purification of PDI, or TRX from extracts or supernatants of said host organisms. This goes also for ENG. Preparation of Trx from natural sources is described by Luthman and Holmgren (Biochem. 121:6628-6633, 1982), Wada and Buchanan (in xe2x80x9cThioredoxins, structure and functionxe2x80x9d (Gadal, Ed.) Editions du Centre National de la Recherche Scientifique), Porque et al. (J. Biol. Chem. 245:2362-2379, 1970) and by Laurent et al. (J. Biol. Chem. 239:3436-3445), whereas recombinant production of TRX is described by Krause et al. (J. Biol. Chem. 266:9494-9500). PDI or sulfhydryl oxidase has been prepared from natural sources by Lambert and Freedman (Biochem J. 213:225-234, 1983), Starnes et al. (U.S. Pat. No. 4,632,905) and Hammer et al. (U.S. Pat. No. 4,894,340), and by recombinant technology by among others Yamauchi et al. (Biochem. Biophys. Res. Commun. 146:1485-1492, 1987). Finally, recombinant production of an ENG is described by Lundstrxc3x6m et al. (J. Biol. Chem. 267:9047-9052, 1992).
The present inventors have succeeded in cloning a DNA sequence encoding a fungal protein disulfide isomerase from filamentous fungi and in obtaining expression of an active protein disulfide isomerase from said DNA sequence, both in the same species and in other organisms, especially microorganisms, and preferably in fungi.
Accordingly, in a first aspect the present invention relates to an active protein disulfide isomerase obtainable from filamentous fungi, specifically fungi belonging to the genus Aspergillus, and especially a protein disulfide isomerase obtainable from A. oryzae, or A. niger, which enzyme is immunologically reactive with an antibody raised against a purified protein disulfide isomerase derived from Aspergillus oryzae, IFO 4177, or Aspergillus niger, A524.
From the sequence of the isolated enzyme it can be seen that the protein disulfide isomerase has two -Cys-X-Y-Cys- subunits in positions 58-61 and 393-396. The invention consequently also comprises active truncated forms of the enzymes of the invention, wherein at least one subunit is retained. Examples hereof could be an enzyme having an amino acid sequence corresponding to the residues 20 to 100, residues 330 to 450, or residues 360 to 430 of the appended SEQ ID No. 3, or the corresponding sequence of the enzyme of the invention in question.
Under this aspect, the invention specifically relates to enzymes exhibiting protein disulfide isomerase activity comprising the amino acid residues 1-131, 1-141, 1-143, 1-163, 1-174, or 1-281, of the amino acid sequence shown in the appended SEQ ID No. 3, or variants thereof exhibiting a protein disulfide isomerase activity. Further specific enzymes are enzymes exhibiting protein disulfide isomerase activity comprising the amino acid residues 1-115, of the amino acid sequence shown in the appended SEQ ID No. 3 extended with the following sequence: Leu-Ile-Arg-Glu-Leu-Leu-Gln-Glu-Leu-Val-Asn-Lys-His-Leq (SEQ ID NO. 11); and an enzyme comprising the amino acid residues 1-511, of the amino acid sequence shown in the appended SEQ ID No. 3, and wherein the amino acid residue in position 511 is changed from Glu to Ala.
In the present context, the term xe2x80x9cderived fromxe2x80x9d is intended not only to indicate a protein disulfide isomerase produced by strains IFO 4177 or A524, but also a protein disulfide isomerase encoded by a DNA sequence isolated from these strains such as indicated in SEQ ID No. 1 and SEQ ID No. 2, or a sequence homologous thereto encoding a polypeptide with protein disulfide isomerase activity and produced in a host organism transformed with said DNA sequence.
Accordingly, the present invention thus relates to an enzyme exhibiting protein disulfide isomerase activity, which enzyme is immunologically reactive with an antibody raised against a purified protein disulfide isomerase derived from Aspergillus oryzae, IFO 4177.
In the present context, the term xe2x80x9chomologuexe2x80x9d is intended to indicate a polypeptide encoded by DNA which hybridizes to the same probe as the DNA coding for the protein disulfide isomerase enzyme under certain specified conditions (such as presoaking in 5xc3x97SSC and prehybridizing for 1 h at xcx9c40xc2x0 C. in a solution of 5xc3x97SSC, 5xc3x97Denhardt""s solution, 50 mM sodium phosphate, pH 6.8, and 50 xcexcg of denatured sonicated calf thymus DNA, followed by hybridization in the same solution supplemented with 50 xcexcCi 32-P-dCTP labelled probe for 18 h at xcx9c40xc2x0 C. followed by washing three times in 2xc3x97SSC, 0.2% SDS at 40xc2x0 C. for 30 minutes). More specifically, the term is intended to refer to a DNA sequence which is at least 70% homologous to the sequences indicated above encoding the protein disulfide isomerase of the invention. The term is intended to include modifications of the DNA sequences indicated above, such as nucleotide substitutions which do not give rise to another amino acid sequence of the protein disulfide isomerase but which correspond to the codon usage of the host organism into which the DNA construct is introduced or nucleotide substitutions which do give rise to a different amino acid sequence and therefore, possibly, a different protein structure which might give rise to a protein disulfide isomerase mutant with different properties than the native enzyme. Other examples of possible modifications are insertion of one or more nucleotides into the sequence, addition of one or more nucleotides at either end of the sequence, or deletion of one or more nucleotides at either end or within the sequence.
In the present context the term active protein disulfide isomerase is intended to indicate an enzyme having an activity similar to that of protein disulfide isomerase, i.e. an enzyme capable of catalysing reaction I. The activity may be determined in an assay based on oxidative refolding of reduced Bowman-Birk soya bean inhibitor, e.g. as described in the Materials and Methods section below.
The term xe2x80x9crecombinantxe2x80x9d as used about the protein disulfide isomerase of the invention is intended to indicate that it is produced by a cell transformed with a DNA sequence encoding the protein disulfide isomerase. Thus, the recombinant protein disulfide isomerase may be produced by either its parent organism or another organism.
In a further aspect the present invention relates to a DNA construct comprising a DNA sequence encoding an active recombinant protein disulfide isomerase of the invention as defined above. Such a DNA construct may comprise introns (an example thereof is shown in the appended SEQ ID No. 1) and/or regulatory elements native to the parts coding for the mature protein disulfide isomerase of the invention, or be a cDNA construct comprising only that part coding for the mature protein disulfide isomerase (an example being the appended SEQ ID No.2).
In still further aspects the present invention relates to a recombinant expression vector harbouring the DNA construct of the invention, to a cell which either harbours the DNA construct or the expression vector of the invention, and to a process for the production of a protein disulfide isomerase of the invention, wherein a cell of the invention as described above is cultured under conditions conducive to the production of the protein disulfide isomerase, and the protein disulfide isomerase is subsequently recovered from the culture.
Finally, the present invention relates to compositions comprising the active protein disulfide isomerase of the invention and methods for their use in various applications.